The present invention relates to assembling of eyewear frame fronts, and more particularly relates to a semi-automatic method and apparatus for inserting a lens into a plastic eyewear frame front.
Plastic eyewear frame fronts are very popular due to their relatively low manufacturing cost, durability, and ability to be molded into a wide variety of style choices. Plastic eyewear frame fronts are typically molded into a single unit eyewear frame front which has right and left eye openings wherein respective right and left optical lenses (plano or prescription) are secured. The eye openings each have an eye groove which circumscribes the interior loop of the eye opening and wherein the beveled edge of the lens is fit in the assembled condition.
The present day method of inserting a lens into the eye opening of a plastic eyewear front involves first heating the frame front to temporarily increase its ductility to a point where the eye opening can be stretched open. The stretching of the eye opening is typically accomplished with a device known in the art as a "stretching cone" which is in the basic shape of the eye opening and tapers to an increasing diameter. The eye opening of the heated frame front is placed over the stretching cone and pressed toward the larger diameter end of the cone, thereby stretching the eye opening in a radially outward direction. Once the eye opening is stretched open to a point which is slightly larger than the corresponding diameter of the lens, the frame is taken off the stretching cone and the lens is manually pressed into the eye opening. The same stretching and pressing steps are lens is manually pressed into the eye opening. The same stretching and pressing steps are repeated for the opposite eye opening. As the frame front quickly cools, the eye openings shrink back to their unstretched state which radially compresses the eye opening about the lens, thereby securing the lens within its respective eye opening.
The above-described method of inserting a lens into a plastic frame front requires the worker to manually work the frame front to first stretch the eye openings thereof, and second to press the lens into the eye opening which must be done quickly so the lens edge is fit entirely within the eye groove before the eye opening has cooled and shrunk back to its original, unstretched state. Problems associated with this manual assembly method are numerous. Pressing of the lens within the eye opening requires manual manipulation of the frame front about the eye opening to urge and direct the lens edge within the eye groove about the full perimeters thereof. The frame front can be quite hot as it is removed from the frame front heating unit and workers many times burn their hands as they press the frame front over the stretching cone and then try to work the lens within the eye opening. Additionally, the manual manipulation of the frame front to press the lens within the opening is strenuous and requires a great deal of finger and wrist movement. Since one worker may handle over 600 frame fronts in one eight hour shift, the number of repetitive motion injuries to worker's hands and wrists is very high. Furthermore, the incidence of accidentally damaging a frame while attempting to insert a lens therein is very high due to the inherent inconsistency of manually working each frame.